Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$100.64	5.797%	$106.4741	$106.47	$106.45	$106.50
Purchase #2	$166.78	7.205%	$178.7965	$178.80	$178.80	$178.80
Purchase #3	$105.33	6.191%	$111.851	$111.85	$111.85	$111.90
Purchase #4	$240.59	6.475%	$256.1682	$256.17	$256.15	$256.20
Purchase #5	$131.58	4.216%	$137.1274	$137.13	$137.15	$137.10
Purchase #6	$41.44	4.808%	$43.4324	$43.43	$43.45	$43.40
Purchase #7	$22.29	11.468%	$24.8462	$24.85	$24.85	$24.80
7 purchase totals =	$808.65		$858.6958	$858.70	$858.70	$858.70